1. Field of the Invention
The present invention relates to a sealed connecting box for fitting a tube to a smooth or screw-threaded aperture of a wall and, more particularly, a connecting box with gaskets of a ringed conduit for protecting a bundle of electric wires in a wall aperture through which the wires pass, this box possibly also being used for the direct sealed passage of an electric cable or a tube through this aperture.
2. Description of the Prior Art
Ringed tubes, that is those of which the shape resembles a succession of interconnected rings, are usually produced from plastics material such as extruded polypropylene. These tubes allow the production of complex networks of protective sheaths for bundles of electric wire or cables within a building, an aircraft or a car, in particular in the engine compartment. In fact, in view of the small amount of space available, these sheaths or pipes must be able to follow non-rectilinear walls closely and to skirt round the various elements encountered. With these tubes it is possible to produce curves of which the radius of curvature is smaller than twice their diameter without the curves being deformed inwardly or even breaking.
To connect such a tube to the aperture of a wall, it is normal to use a stuffing box consisting of five parts: a tubular body with a front thread and a rear thread separated by a supporting flange, an internal gripping joint, a bushing nut engaging on the rear thread of the body and gripping the joint against the central ringed tube, a circular crown-shaped joint being interposed between the flange of the body and the rear face of the wall and, finally, a flat nut engaged at the front of the wall on the front thread of the body once the body has passed through the aperture. A stuffing box of this type is described in the document EP-A-0 515 200.
In order to fit this stuffing box correctly, the bushing nut and the gripping joint are first slipped over the ringed tube and the wires. The circular joint is then fitted on the body, the front portion of which is screwed into the wall to be traversed in order to compress this joint. The wires can then be passed through the body and the flat nut which is then screwed on the front portion of the body to prevent this body from being released from the wall. The ringed tube can then be inserted in the rear portion of the body and the gripping joint is brought into contact therewith. Finally, the bushing nut can be brought into contact with the gripping joint and this nut can be screwed on the rear portion of the body while compressing and deforming the joint, simultaneously producing the seal and the tensioning of the ringed tube in the body.
Although the strength of the ringed tube is relatively satisfactory with regard to the seal between, on the one hand, the external environment and, on the other hand, the interior of the ringed tube and the rear zone of the wall which frequently corresponds to the internal space of a box which is itself sealed, it is noted that it is directly linked to the gripping force of the bushing nut which, in practice, is never constant. In particular, installation of this stuffing box as described hereinbefore is time-consuming and awkward because, as the parts are circular, they are fitted by being slipped through. Furthermore, there is a risk that one of the parts, in particular the gaskets, will be forgotten or lost. Finally, stuffing boxes are expensive to use insofar as a stock of five parts each having a distinct reference has to be supplied and maintained.
To this end, the document EP-A-0 442 505 proposes a plastic connecting box for undulating pipes having the form of two shells which are substantially symmetrical about a plane passing through the longitudinal median axis of the ringed tube, said shells being folded round a hinge in the form of a film of connecting material along a common longitudinal joining face. These shells are each provided with a hook and a locking window located on the longitudinal joining face opposite that of the hinge, the hook engaging in the window when the shells are folded over one another in their median joining plane. Once closed, this connecting box has a rear section intended to accommodate the end of the ringed tube, the internal space of this section comprising transverse ribs which are interposed between the grooves of the tube in order to retain it. This section is extended at the front by a smaller diameter sleeve having an external thread designed to be passed through the aperture in the wall. The interface between the rear section and the front sleeve forms a circular crown-shaped surface for supporting the box against the wall.
Furthermore, a nut is provided which is also in the form of two semicircular elements connected on one side by a film hinge and locked on the other side by a hook engaging in a window. In order to rigidify this nut once the elements are closed, a six-sided external shell of which one of the sides is open for passage over the electric cables and wires is placed on the periphery.
Although this connecting box is easier to fit as it no longer has to be slipped through but can be closed round electric cables and lines, there is no gasket between the box and the wall nor between the tube and/or cables and the box. Therefore, this box cannot be used in difficult damp and/or dusty environments. Furthermore, it should be noted that the nut is supplied separately from the box.